JP3934876B2 - Method for producing reinforced three-band microporous membrane - Google Patents

Description

【００７７】
実施例１
「開放」（大きな孔サイズ）スクリム含浸を伴う、幾何学的に対称的であり、孔サイズ対称的な連続した３帯膜は、以下のように準備された。
【００７８】
不織布ポリプロピレン異相構造繊維ウェブまたは本発明（Viledon, Grade # F02432のFreudnbergで市販で入手可能）の準備に適したスクリムは、名目上３０グラム／平方メートルの基本重量を有しており、本出願に教示される方法によって処理された。スクリムは、ゆるやかなコロナ放電で前処理され、圧力含浸される前に湿潤性を高める。より大きな孔サイズドープ９７Ｌ０３８は、ウェブに、約７グラム／平方メートルの含浸重量ナイロン固体で圧力含浸するのに用いられた。ナイロン固体は、ドープ溶液内で溶解したナイロンからもたらされる。該ドープ溶液は、例えば、１４．５％のナイロン溶液（およそ１平方メーターにつき５０グラムの流体ドープ）であり、該量の溶液は、ボイド量を含浸し、充填して、保持スクリムと一体化した大きな孔サイズの第１帯を造る。９７Ｌ０３８ドープでスクリムを圧力含浸させてすぐに、圧力含浸させたスクリムの両側が、本質的に同時に小さな孔サイズドープ、９７Ｌ０２８の一様な層で被覆される。上記例において、２側面に運ばれる被覆重量全体は、１４．５％の溶液（１平方メーターにつきおよそ２６０グラムの流体ドープ）内に約３７グラム／平方メートルのナイロン固体であり、被覆重量全体は、２側面上に送り込む２流のドープに分れる。これによって、両側面は、実質的に一様に同一のドープで被覆され、小さな孔サイズドープの第２帯及び第３帯を造る。含浸されたスクリムの片側がおよそ１５グラム／平方メートルのナイロン固体を受け、もう片方がおよそ２２グラム／平方メートルのナイロン固体を受け取るという点で、９７Ｌ０２８ドープの量の分割は完全ではなかった。２側面上の被覆されたドープ量が不均衡であることは、結果的に被覆する帯を確定する小さな孔サイズに、わずかな不均衡をもたらすが、該不均衡は、最終製品の性能に不利益をもたらさない。両方のドープの全適用が、およそ４４グラム／平方メートルナイロン固体であった。被覆された３帯の構造体は、その後、マリナコ型の冷却溶液と素早く接触する状態になる。小さな孔サイズドープである、９７Ｌ０２８の外面から３帯構造体を同時に冷却する。それによって、連続微孔性膜構造体が形成された。冷却された膜は、その後、洗浄され、Ｘ＆Ｙ方向の寸法安定性で乾燥され、通常の方法でテストされた。テスト結果は、表２に示される。
【００７９】
図４a−４fは、実施例１で造られる膜の断面の電子顕微鏡写真である。
【００８０】
実施例２
幾何学的に対称的で、孔サイズが非対称的な３帯の膜は以下のように準備された。
【００８１】
第２の３帯膜は、圧力含浸されるスクリムの被覆面の１面が大きな孔サイズドープ９７Ｌ０３８から同一のおよそ２２グラム／平方メートルのナイロン固体で被覆されるということを除いて、実施例１とほとんど全く同じ方法で準備される。対向側（（ゾーン３）は、小さな孔サイズのドープ９７Ｌ０２８からおよそ２２グラム／平方メートルのナイロン固体で被覆された。２面を同時に冷却し、洗浄し、制御乾燥した後、結果として生じる最終膜は、連続した、補強スクリムの中立軸に実質的に幾何学的に対称になるが、スクリムの両側に非常に異なる孔サイズの特質を有する。（例えば、孔サイズ非対称）上記膜のテスト結果も表２に示される。
【００８２】
図５a−５fは、実施例２で造られる膜の断面の電子顕微鏡写真である。
【００８３】
実施例３
制御し、補強された膜（単一ドープ、３帯）が準備された。
【００８４】
本出願の方法に従って造られる補強された膜と比較して、制御し、補強された膜が造られた。この３帯の、補強された膜は、圧力含浸された第１帯が小さな孔サイズドープ９７Ｌ０２８を用いて造られたということを除いて、実施例１で造られた膜と全く同一である。したがって、３帯のすべてが、単一ドープを用いて造られ、各々のダイへ３流に分割される。２面を同時に冷却し、洗浄し、制御乾燥した後、結果として得られる膜は、連続し、実質的に幾何学的対称な、単一孔サイズ構造膜であった。該膜は類似形であり、今日のナイロン微孔性膜産業に共通の標準的単一層補強膜に作用する。上記膜のテスト結果も表２に示される。
【００８５】
【表２】

【００８６】
実施例１から実施例３
表２からわかるように、実施例１の膜は、標準的な膜より明らかに改良された流量を有する。純水流量（水圧５psidにおいて名目上４７mmテストディスク（１３．５ｃｍ²テスト領域）に対してcc/minの清潔なイオン除去された水を表すＱ）は、約２０％の改良を示しているが、全体的に同一な厚さにおいて、初期バブルポイントで測定される集結度は約６％増加した。上記改良は、潜在的に２つの利点を備えている。該利点とは、改良された清潔な水流量と、ＩＢＰによって測定された改良された集結度である。初期バブルポイントの増加は、膜の全発泡ポイントの増加及び、ＡＳＴＭ平均流孔サイズ率の減少の両方で確証される。
【００８７】
実施例１の膜は、本発明の利点を表している。小さな孔サイズ膜の２つの幾何学的対称な、独立した、独自の確定帯が存在し、余剰な確定層による最も高い集結度をもたらし、非制限内帯で分離される。非制限内帯は、補強部を包含し、確定層の性能が低下することなく、全体的に驚くほど薄い断面になる。
【００８８】
実施例２の膜は、約７８パーセントの標準（制御）膜よりも流量において素晴らしい改良がなされたが、ＩＢＰ及びＦＡＯＰにおいて同一の集結特性を保つ。より一般的に認識される方法である、平均孔サイズ（ＭＦＰ）は、ＦＡＯＰが近似する平均流孔（ＭＦＰ）の平均孔サイズであり、予想差異を示す，大きな平均流孔になればなるほど、より高い流量と一貫しており、制御膜と比較すると、流量平均方法によれば、実施例２の膜の孔サイズは、より広く分布することが示される。しかしながら、膜上の単一最大孔のレーティングであると同時に、精密濾過産業が膜の完成度をテストするために基づいている基準である、同一の初期バブルポイントを有し、流量の改良点の重要性を減じない。したがって、実施例２は、本発明の膜におけるもう１つの利点を示している。該利点とは、孔サイズを低減させるとき、新たな、驚くほど薄い断面結合の補強された未濾過及び最終濾過をもたらし得る性能を有する。該性能とは、単一膜内で３つの分離した帯を作る能力であり、幾何学的に対称であり、良い集結度及び非常に高い流量を備えている。
【００８９】
実施例４
本実施例で用いられるドープは、最初の３つの実施例のように準備された。ドープは、ナイロン６６（Monsanto/Solutia Vydyne 66Z）ポリマーを用いて造られた。標準的で乾燥した２層の補強されていない膜として加工される上記ドープの特徴は、表３に与えられる。
【００９０】
【表３】

【００９１】
「開放」（大きな孔サイズ）スクリム含浸を伴い、もう１つの幾何学的に対称的であり、孔サイズが対称的な、補強された３帯の膜が、準備された。
【００９２】
本発明（アールストロム、トレードネーム ホリテックス）（Ahlstrom, tradename Hoolytex, Grade #3257から市販で入手可能）の準備に適した不織繊維のスパンボンドされたウェブは、名目上３２グラム／平方メートルの基本重量を有し、加工用に選択された。加工方法は、本質的に実施例１に開示されている方法と同一であった。相違点は以下であった。約６グラム／平方メートルのナイロン固体の含浸重量を有する大きな孔サイズドープ９７Ａ０１６を用いて１帯を圧力含浸する。２帯及び３帯は、本質的に同時に、小さな孔サイズドープである、９７Ａ０１２の実質的に一様な層で被覆された。この実施例において、２側面に運ばれる全体の被覆重量は、約１９グラム／平方メートルのナイロン固体であり、この全体量は、２側面に実質的に均一に分割され、その結果両方の帯は、約８から約１１グラム／平方メートルの被覆を受けた。冷却、洗浄及びテストは、前記実施例にあるようである。上記膜のテスト結果は、表４に示される。同時に、制御膜が加工され、２帯及び３帯だけでなく、１帯でも小さな孔サイズドープ９７Ａ０１２を用いた。制御膜のテスト結果も表４に示される。
【００９３】
【表４】

【００９４】
表４の論議
非常に薄い断面を有する３帯の、補強された微孔性膜が上記のように造られた。上記実施例は、補強された帯及び２つの非常に薄い確定帯を明示し、かなり高い集結度膜を備えた。充填されたホリテックス（Hollytex）スクリムの厚さは、およそ３．５ミルであることが留意されるべきである。それ故、実施例４の４．７ミルのうち残りの１．２ミルが２帯及び３帯で分けられ、補強された帯の各側面で約わずかに０．６ミルの有効確定膜が残される。しかしながら、この厚さは、制御膜に比べると、約５５パーセントの流量改良が可能で、わずか約１２パーセントの集結度を損失するだけである。
【００９５】
実施例５
本実施例に用いられるドープが、上記のように準備された。ドープはナイロン６６（Monsanto/Solutia Vydyne 66Z)を用いて造られた。標準的な乾燥した２層の非連続膜として加工されるドープの特徴が表５に与えられる。
【００９６】
【表５】

【００９７】
「開放」（大きな孔サイズ）スクリム含浸を伴い、もう１つの幾何学的に対称的で、孔サイズが対称的な、補強された３帯の膜は、以下のように準備された。
【００９８】
同一の基質が、実施例４（Hollytex 32547）に用いられ、加工方法は、本質的に実施例１に開示される方法と同一であった。しかしながら、ゾーン１（Zone one)は、含浸重量が約６グラム／平方メートルのナイロン固体を有する大きな孔サイズドープ９７Ｂ０１１を用いて圧力含浸された。２帯及び３帯は、小さな孔サイズドープである９７Ｂ０２４の実質的に一様な層で被覆（coated)された。本実施例において、２側面に運ばれる被覆重量全体は、約３８グラム／平方メートルのナイロン固体であった。運ばれた全体的な被覆重量が、２側面間に分割された結果、両方の層２帯及び３帯は、約１７から約２１グラム／平方メートルのナイロン固体被覆加工を受けた。両方のドープ（大きな孔サイズ及び小さな孔サイズ）の全適用は、およそ４４グラム／平方メートルのナイロン固体であった。冷却、洗浄、乾燥、及び、テストは、前述のように行われた。得られた膜のテスト結果は、表６に示される。同じ実験中に、３帯すべての中の小さな孔サイズドープ９７Ｂ０２４を用いて、制御膜が加工された。制御膜のテスト結果も表６に示される。
【００９９】
【表６】

【０１００】
実施例５の議論
表から見てわかるように、実施例４と比較して、本実施例である実施例５の確定帯２及び３を形成するのに用いられる名目上のより高い被覆重量は、高い集結度の膜を生成する。当該膜は、制御膜の約５パーセント内のＩＢＰ、及び制御膜と比較すると、約５３パーセントの流量改良を備える。
【０１０１】
実施例６
ドープが前記のように準備された。ドープは、ナイロン６６(Monsanto/Solutia Vydyne 66Z)ポリマーを用いて、造られた。標準的な乾燥した２層の非連続膜として加工されるドープの特徴は、表７に与えられる。
【０１０２】
【表７】

【０１０３】
「開放」（大きな孔サイズ）スクリム含浸を伴い、さらにもう１つの幾何学的に対称的で、孔サイズが対称的な、補強された３帯の膜が、準備された。
【０１０４】
実施例４と同じ基質が用いられた（Hollytex^R 3257) 。加工方法は、実施例１に開示された方法と同じであった。しかしながら、１帯は、約６グラム／平方メートルのナイロン固体の含浸重量を有する大きな孔サイズドープ９７Ｂ０６７を用いて、圧力含浸された。２帯及び３帯は、同時に実質的に一様な小さな孔サイズドープ、９７Ｂ０６６の層で被覆された。本実施例において、２側面に運ばれる全体の被覆重量は、約２４グラム／平方メートルであった。運ばれる全体の被覆重量は、２側面間で分割された。これによって、両方の帯は、約１１から１３グラム／平方メートルのナイロン固体膜を得た。両方のドープの全体適用は、およそ３０グラム／平方メートルのナイロン固体であった。冷却、洗浄、乾燥及びテストは、前記例のように行われた。この膜のテスト結果は、表８に示される。同じ実験中、３帯すべての中の小さな孔サイズドープ９７Ｂ０６６を用いて、制御膜は加工された。制御膜のテスト結果も表８に示される。
【０１０５】
【表８】

【０１０６】
実施例６の議論
再び、実施例４と比較すると、本実施例における確定帯２及び３の名目上より高い被覆重量は、集結度の非常に高い膜を生成する。当該膜は制御膜の約１パーセント内のＩＢＰを備え、制御膜より約３５パーセント改良された流量を備える。
【０１０７】
上記の特有の実施例は、０．１ミクロンの膜を示しており、エレクトロニクス産業における、半導体及び集積回路製造用の水を浄化する際に使用するのに適している。本出願に記載された新たな加工の結果として生ずる、新しい膜の清潔水の流量が増加することで、半導体生産工場を建設する際に、より小さなデザインで、費用のかからない処理システムが可能になり、デザインディマンド流量において同じ高品質の最終水をもたらす。
【０１０８】
実施例の概要
本発明の３帯の膜は、膜濾過産業に一般的な標準的製品と比較すると、孔サイズの特性のために、濾過適用で流量を著しく改良したことを特徴とする。３帯の比較的薄い断面、膜製品によって、より大きな表面積及びさらに高い処理能力を有する膜カートリッジを得る。これによって、濾過の顧客のために、さらに高い価値のある追加製品へと変えられる。
【０１０９】
基質のごく一般的な実験、前処理、帯被覆重量、ドープ粘度、孔サイズ、及び孔サイズに関する帯の位置付けによって、最適化された膜製品がもたらされ、該膜製品は、現存する膜製品より優れた性能を備える。帯性能をカスタマイズする能力から利益を得る他の膜適用は、（例として）人体流体を用いる診断用製品、移送膜、分離装置、医療装置、及び、膜技術の当業者には明らかなその他の装置を包含する。
【０１１０】
図４a-hにはっきりと示されるように、本発明に従って造られた３帯の、支持付微孔性膜は、３つの別個の、連続した帯を有する。また、図４b-４dにはっきりと示されるように、中心帯内に包含されるスクリムの少なくとも１部が、上方帯及び下方帯（同じ、小さめの孔サイズを有する帯）の両方に少なくとも部分的にはみ出す。
【０１１１】
図５a-hに明らかに示されるように、本発明に従って造られる３帯の、支持付、微孔性膜は、３つの別個の、連続した帯（ゾーン）を備える。また、図５b-５dに明らかに示されるように、中心帯（最大孔サイズを有する帯（ゾーン））内に包含されたスクリムの少なくとも１部が、下方帯（小さめの孔サイズを備える帯）に少なくとも部分的にはみ出す。
【０１１２】
上記に基づけば、流体内のドープを混合させる本発明の方法によって、新たに改良された、３帯の、連続した膜がもたらされる。
【０１１３】
前述に基づけば、ここで記載する３帯の、補強された膜を造るための装置及び課程を用いると、上記目的が遂行されることが明らかである。微孔性膜の第１帯内に少なくとも実質的に埋め込まれ、第１帯の各対向面上に微孔性ポリマー膜の少なくとも１帯（ゾーン）を備える、少なくとも単一層の保持体を有する種々の微孔性膜を製造するために、本発明の課程が実施されるということも、当業者には明らかである。同様に、スクリムが連続して装置に送りだされるスピードだけでなく、ドープ冷却溶液、濃度、温度が、当業者によって容易に決定され得る。
【０１１４】
本発明の３帯の膜は、ポリマーの分離層／帯の連続したもつれを有する不連続孔構造体を備える。これによって、造られた連続した微孔性膜は実質的に一体化する。
【０１１５】
本発明の３帯の、補強された、微孔性膜１０の形成後、該膜は、ここに参照として組み込まれる開示である、米国特許第４４７３４７４号に従って処理され、電子構成要素を製造するのに要される高純度水を濾過するのに特に適した、陽性の電荷改質された微孔性膜を造り、各々の開示がここに参照として組み入れられる。
【０１１６】
他の３重転相ポリマーを用いるとき、本発明が、同一または類似した結果を有するということを立証するための実験は未だ行われていないが、本発明は、同様の化学的構成及び構造体のために、多くの３重転相ポリマーを、膜または他の有用な目的のために加工するのに、有効であると目下のところ信じられている。特に、ナイロン６６は、転相処理によって微孔性膜に加工され得る多くのポリマー基である。これによって、上記課程は、本発明の方法及びシステムが他のポリマーにも適用可能であり可能性が高い。該ポリマーは、ナイロン６６、ナイロン４６、ナイロン６、ポリスルホン、ポリエチルスルホン、ポリビニリデンジフルオリド及び転相課程を通じて微孔性構造体を形成する他の３重転相ポリマーを含むが、限定されない。
【０１１７】
ここに包含されるものを造るためのもの、装置及び方法は、本発明の好ましい実施例を構成するが、正確にそのもの、装置及び方法に限定されることなく、添付した請求の範囲で明示される本発明の範囲からそれることがなければ、変更され得る。
【図面の簡単な説明】
【図１】 本発明による膜の断面図である。
【図２】 本発明の方法および装置の概略図である。
【図３】 図２の相対するダイ間に配置されるウェブの拡大透視図であり、片方のダイの１部が部分的に切断されている。
【図４ａ−ｈ】 本発明の支持付３帯の微孔性膜の電子顕微鏡写真であり、１００Ｘ、３００Ｘ、５００Ｘ、１０００Ｘおよび２５００Ｘにおける３つの孔帯の内面を表す。
【図５ａ−ｈ】 本発明の支持された３帯の微孔性膜の電子顕微鏡写真であり、１００Ｘ、３００Ｘ、５００Ｘ、１０００Ｘおよび２５００Ｘにおける３つの孔帯の内面を表す。
【符号の説明】 １０ 膜、１２，３２ 保持体、１６ 中間帯、１８ 上方又は第２帯、２０ 下方又は第３帯、２２ 第１側面、２４ 第２側面、２６，２８，３６ ドープ、４０，４２，４４ ダイ、７０ すすぎ装置、７２ 逆流動体洗浄タンク、７４ スロット。[0001]
(Technical field)
This application is related to US Provisional Application No. 60/043181, filed April 11, 1997 by publicly owned Mailing et al.
[0002]
Background art
The present invention relates to a continuous, reinforced, geometrically symmetric, microporous membrane having three distinct perforations and the process of making and using the membrane, and more particularly including a scrim. For a reinforced microporous membrane, the scrim has two sides that are at least substantially contained within the first dope, and the at least one additional dope is contained before the first dope is cooled. On each side. The present invention also relates to a geometrically symmetric, continuous, reinforced membrane having at least substantially, and preferably, three distinct perforations comprising a scrim, said membrane being relatively large Completely encompassed by a hole size intermediate band and two outer bands, one side being each side of the intermediate band, at least one of the three bands having a hole size at least about 20 percent greater than the other band, An apparatus for manufacturing a film and processing the film is provided.
[0003]
Microporous phase inversion membranes are well known in the art. The microporous phase inversion membrane is a porous solid and includes microporous interconnecting channels. The passage extends from one surface to the other. The passage comprises a curved tunnel and road. The path passes through the liquid to be filtered. Particles included in the liquid that passes through the microporous phase inversion membrane are trapped on or in the membrane structure that results in filtration. A slight pressure, generally in the range of about 7 to about 50 psid (pound per square inch difference), is used to pass the fluid through the microporous phase inversion membrane. Particles in the fluid larger than the pores are prevented from entering the membrane or confined within the membrane pores, and some particles smaller than the pores are also confined or membrane pores in the curved path of the pores Absorbed by the structure. Fluids and particles that are smaller than the pores of the membrane pass through. Thus, a microporous phase inversion membrane is prevented from passing certain size particles or larger particles, but at the same time several fluids and particles smaller than a certain size can pass. The microporous phase inversion membrane retains particles in a size range of about 0.01 microns or less to about 10 microns or more.
[0004]
Many important micron and submicron sized particles can be separated using microporous phase inversion membranes. For example, red blood cells are about 8 microns in diameter, platelets are about 2 microns in diameter, and bacteria and yeast are about 0.5 microns in diameter or smaller. Bacteria can be removed from the water by passing the water through a microporous membrane having pores smaller in size than the bacteria. Similarly, microporous membranes can remove invisible suspended particles from water used to manufacture integrated circuits in the electronics industry. Microporous membranes are characterized by a bubble point test. The test involves measuring the pressure that pushes the first bubble out of a fully moistened phase inversion membrane (Initial Bubble Point, IBP), which pushes air out through many holes throughout the phase inversion membrane Related to measuring pressure (total foaming point, or FAOP). The initial bubble point and FAOP test is described in US Pat. No. 4,645,602, issued February 14, 1987, the disclosure of which is hereby incorporated by reference. The initial bubble point test and the more general average hole test are detailed, for example, in ASTM A316316-70 and ANS / ASTM F316-70 (Recertification 1976), which are incorporated herein by reference. Bubble point values for microporous phase inversion membranes generally range from about 5 to about 100 psig, depending on the pore size and wetting fluid.
[0005]
US Pat. No. 3,876,738, the disclosure of which is incorporated herein by reference, describes a process for preparing a microporous membrane by cooling a solution of a film-forming polymer in a non-solvent system for the polymer. U.S. Pat. No. 4,340,479, the disclosure incorporated herein by reference, generally discloses a bare microporous polyamide membrane by casting a polyamide resin solution onto a substrate and cooling the resulting thin film of polymer. To prepare.
[0006]
Since the mechanical strength of microporous membranes is inferior, it is known to reinforce the membrane with a porous support, improve mechanical properties, and facilitate processing and processing. Thus, the aforementioned U.S. Pat. No. 4,340,479 discloses that a polymer solution is cast directly into a porous support so that the polymer solution penetrates the support during casting and provides a reinforced inner layer of a synthetic microporous membrane. A method is described that adheres firmly during formation. The holding body preferably has an open structure. This minimizes the pressure drop across the synthetic membrane. U.S. Pat. No. 4,340,479 further discloses two or more microporous membranes, one of which binds a reinforced microporous membrane to form a two-layer or three-layer structure. It is disclosed. The structure is dried under constraining conditions to produce a single sheet with better particle removal characteristics than the individual layers.
[0007]
U.S. Pat. No. 4,707,265, the disclosure of which is incorporated herein by reference, discloses a reinforced, laminated filtration membrane that is impregnated with a polymeric microporous inner membrane. And at least one porous outer definite membrane laminated to each side of the impregnated web. The pore size of the inner membrane is larger than the pore size of the outer membrane. In this way, imperfections that are necessarily present in the reinforcing web, such as fiber bundles, torn fibers, void areas and the like, are limited in the coarser, more open inner membrane, and the denser definite outer layer is , Reinforced and supported by the web. The deterministic layer is not affected by imperfections present in the reinforcing web. Furthermore, the use of a coarse, large pore size inner membrane layer ensures that there is no substantial pressure drop of fluid across the reinforcing web.
[0008]
The membrane disclosed in US Pat. No. 4,707,265 is complex and expensive to build because it requires three individual operations to make a synthetic membrane. That is, firstly, an impregnated and reinforced membrane retention layer is created, secondly, a non-reinforced, definite layer is created, and third, impregnated and reinforced membrane retention layer and unreinforced. The deterministic layer is laminated to form a multilayer synthetic microporous membrane.
[0009]
There is a limit to how thin the retaining layer of impregnated and reinforced membranes and the unreinforced deterministic layer can be to process and process the inhibitor. As a result, the multilayer synthetic microporous membrane of US Pat. No. 4,707,265 is at least about 10 mils thick. Further, the overall pore size of the synthetic membrane described in US Pat. No. 4,707,265 is approximately approximately because it is difficult to separately create and process unreinforced deterministic layers having pore sizes on the order of about 0.45 microns. Limited to a range of 0.45 microns or less. Thus, the use of laminated synthetic membranes is limited to application sterilization and other applications where membranes with micron ratios of about 0.65, 0.8, 1.2, 3.0 and higher are not required. Is done.
[0010]
As the thickness of the membrane increases, the pressure drop increases, the flow rate worsens, and the performance characteristics of the membrane are adversely affected. For example, increasing the thickness reduces the overall number of pleats in the pleated cartridge element, thereby reducing the useful surface area for filtration. In addition, mechanical tension exists at each pleat crest and increases with increasing thickness. As a result, thick membranes are prone to cracking during operations associated with the manufacture of pleated filtration cartridge elements, such as during pleating, edge seam stitching, or during multiple cycles of oxidative hydrolysis or steam. Therefore, the mechanical tension is not sufficiently reduced after the cartridge is manufactured, but it shortens the shelf life of the product and quickly disturbs the concentration.
[0011]
U.S. Pat. No. 4,770,777 immerses a reinforcing web in a large pore size membrane casting solution and applies a small pore size membrane casting solution on one side of the web to be coated, from one side to a large pore size casting solution and Cooling the small pore size casting solution to provide a continuous, geometrically asymmetric membrane with a pore size gradient overcomes the disadvantages of the process disclosed in US Pat. No. 4,707,265. Thus, the lamination step of U.S. Pat. No. 4,707,265 is omitted, along with the need to process brittle and unreinforced definite membranes. Furthermore, in accordance with the teachings of the above patent, it is impossible to apply another casting solution on the other side of the large pore size reinforced web containing the layer. Thus, only the added layer can be cast on the second layer cast on the first layer containing the assembled material. Further, the membrane shown in US Pat. No. 4,770,777 is a bare membrane. Thus, the membrane suffers from defects associated with the bare microporous membrane. In particular, there is a tendency to get tangled by high pressure drop, poor structure concentration, skin laceration, and debris.
[0012]
U.S. Pat. No. 5,433,859 preferably incompletely impregnates the reinforcing web with a coarse membrane casting solution so that a portion of the reinforcing web having a thickness of about 50 microns is embedded within the microporous membrane. By not doing so, it attempts to address some of the bare film defects disclosed in US Pat. No. 4,770,777, particularly high pressure drops. The low flow resistance in that portion of the reinforcing web that is not embedded within the microporous membrane ensures that the filtered fluid through the supported microporous membrane does not adversely affect the pressure drop across the filtration element. Become.
[0013]
Although the membrane disclosed in U.S. Pat. No. 5,433,859 has been shown to have a lower pressure drop across the membrane as compared to the bare membrane disclosed in U.S. Pat. No. 4,770,777, it is a structurally significant defect. Does not have. First, the membrane is geometrically asymmetric about the central axis of the reinforcing web, i.e., the thickness of the membrane varies on each side of the reinforcing web. As a result, when the membrane is pleated, the mechanical tension on the thick side of the membrane is greater than the tension on the thin side of the membrane. The difference in the mechanical tension increases the possibility of cracking due to stress and the possibility that the degree of film concentration decreases. Secondly, there is a risk that the membrane will separate along the membrane reinforcing web connector, especially during backwashing. Third, the membrane exhibits “sidedness” with different pore sizes on one side relative to the other side and on the exposed scrim reinforcement area. This limits its use in certain applications, such as analytical or diagnostic filtration techniques. Finally, like U.S. Pat. No. 4,720,777, the membrane of U.S. Pat. No. 4,433,859 cannot have another cross section on the opposite side of the membrane reinforcing web for the same reason as U.S. Pat. No. 4,770,777. is there.
[0014]
Thus, at least three independent, distinct pore size work zones (one reinforced work zone is currently preferably central to the membrane structure and the two outer unreinforced work zones are At least one outer definite work band and a second outer non-definite work band on the other side of the central work band, or two outer definite work bands, and one band on each side of the central band. There is a need for a relatively thin, geometrically contrasting, continuous, monolithic, reinforced, polymeric microfiltration membrane with advancing through the thickness of the membrane, Each band is continuously joined to the entire membrane structure. The three bands are joined sequentially by molecular entanglement that occurs in the liquid state of the dope after each outer band dope is coated with the central band dope before cooling, rather than by a laminate bond after cooling. . The three-zone membrane structure can be made by very strong single device operation with on-line pore size and layer thickness property control. The three-band membrane meets the industry's long recognized demand for better performance and higher flexibility of a three-layer composite structure. Each of the three band films is prepared inexpensively. The three-band membrane simplifies the manufacture of an aggressive laminated single layer structure membrane and increases the processable thickness provided by the pore size range and the unreinforced band. The three-band membrane avoids the highly geometrically asymmetric structure of the conventional two-band membrane. The three-band membrane is geometrically symmetric, ensuring structural integrity, improved utility, flexibility and ability to process into final industrial forms (such as pleated cartridges) It has a structure. The three membranes have surprisingly thin cross-sections and three individual working zones within a geometrically symmetrical, continuous, monolithic, reinforced, polymeric, microfiltration membrane. The device of the present application was filed on Feb. 11, 1998, which is hereby incorporated by reference and disclosed herein as “a number of different microporosities, each having any one of a number of different pores. When joined to co-pending application 09/022295 by the same assignee entitled “Method and System for Making a Conversion Film”, the three-band film has strong mechanical force and is pleated And industrially suitable and can be built online in real time with a surprisingly wide range of pore size characteristics. The three-zone membrane has a minimum functional drop resulting in maximum throughput, high concentration with minimal pressure drop, and is economically made in a single manufacturing operation.
[0015]
Summary of the Invention
One object of the present invention is to provide a three-band, reinforced, continuous, unlaminated, geometrically symmetric microporous membrane with structural integrity.
[0016]
Another object of the present invention is to provide a three-zone, reinforced, continuous, unlaminated symmetrical microporous membrane that exhibits low pressure drop and high flow across the membrane.
[0017]
Yet another object of the present invention is to provide a three-band, reinforced, continuous, unlaminated, geometrically symmetric, microporous membrane, which is particularly biological. Or it is suitable for the filtration of parenteral liquids.
[0018]
Yet another object of the present invention is to provide a three-band, reinforced, continuous, unlaminated, geometrically symmetric, microporous membrane. The membrane is particularly suitable for filtering high purity water for the electronics industry.
[0019]
Yet another object of the present invention is to provide a method of making a three-band, continuous, reinforced, unlaminated, geometrically symmetric microporous membrane.
[0020]
Another object of the present invention is to provide an apparatus for producing a three-band, continuous, reinforced, unlaminated, geometrically symmetric microporous membrane.
[0021]
In accordance with the above and further objects, one aspect of the present invention includes the step of forming a three-band, continuous, reinforced microporous membrane. The process includes the following steps. That is, a continuous holding body having a first side surface and a second side surface is prepared; the first die relating to the holding body is arranged to function; and the first die means is used to form a three-band microporous membrane. At least substantially pressure impregnating the support with a first polymer dope to produce a first pore size in the intermediate zone; two die means located substantially opposite the first die means Passing at least a substantially polymer-doped pressure impregnated carrier between the substantially opposite second and third die means, whereby the first polymer-doped To cover both sides of the supported carrier substantially simultaneously with at least one additional polymer dope to produce at least one additional pore size in two other bands of the three-band microporous membrane, Virtually opposite It utilizes two of die means to be.
[0022]
Another aspect of the invention is a method of making a three-zone, reinforced, continuous, geometrically symmetric microporous membrane, the membrane being produced by the following steps. That is, a porous holder having first and second sides is prepared; first, the holder is at least substantially impregnated with the first dope; and the second dope is coated on the first side of the impregnated holder Coating a third dope on the second side of the impregnated carrier. This forms a continuous microporous membrane with an intermediate band located between the upper and lower bands of the first, second and third dopes. The retainer is at least substantially embedded in an intermediate band, the intermediate band having a pore size that is at least about 20 percent greater than the pore size in at least one of the three bands.
[0024]
Other objects and advantages of the invention will become apparent from the following description, accompanying drawings and claims.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
As shown in FIG. 1, one exemplary, presently preferred, three-band, reinforced, continuous, non-laminated, geometrically symmetric microporous membrane 10 comprises: It is built based on the process of the present invention. The membrane 10 includes a hole support element or scrim 12 substantially contained at least in the middle, or first zone 16. The intermediate band is disposed between the upper or second band 18 and the lower or third band 20. The holding body 12 is at least substantially embedded in the intermediate band 16. The middle band comprises a hole size that is at least about 20 percent greater than the hole size in at least one of the upper band 18 and the lower band 20. Although the above structure of the membrane is presently preferred, the hole size of the intermediate band need not necessarily be the maximum hole size, and any one of the three bands is from the maximum manufacturable hole size to the minimum manufacturable hole size. If it is in range.
[0026]
As used herein, the term “microporous membrane” refers to a microporous membrane having the ability to retain particles in a size range of about 0.01 microns or less to about 10.0 microns or greater. It means to include.
[0027]
It is understood that the term “continuous” as applied to the microporous membrane of the present invention refers to a microporous membrane. In the microporous membrane, there is a continuum between the three zones constituting the membrane, and there is a gap between the polymer structure including the intermediate zone and the polymer structure including the upper zone and the lower zone of the membrane. Absent. The microporous membrane structure is a continuous structure in which reinforcing scrims are uniformly present, and the fiber strain of the scrim constitutes a network structure through which the microporous membrane is continuous. Therefore, the scrim and the microporous membrane form a continuous, fully permeable network of each polymer structure.
[0028]
The term “monolithic” as applied to the present invention means a single unit.
[0029]
As used herein, the expression “geometric symmetry” is understood to describe a structure in which the upper pair and lower band of microporous membranes have substantially the same thickness. By “substantially the same thickness”, it is meant that the thickness of the upper band can differ from the thickness of the lower band by less than 25 percent and vice versa. It is important to compare the meaning of the term “symmetric” as used herein with the meaning of “symmetric” as used in US Pat. No. 4,707,265. In that patent, it is used to describe that the pore sizes are symmetric; therefore, in US Pat. No. 4,707,265, the term applies when the outer deterministic layer comprises substantially the same pore size. In certain embodiments of the present invention, symmetric pore size is a highly preferred feature of the inventive progressive microporous membrane, but is not essential.
[0030]
The term “pore size” in this application is understood to mean “average flow pores” as determined by appropriate ASTM-F316-70 and / or ASTM-F316-70 tests.
[0031]
Preferably, the microporous membrane of the present invention is hydrophilic. By using the term “hydrophilic” to describe a membrane, it means a membrane that adsorbs, that is, absorbs water. Generally, a sufficient amount of hydroxyl group (OH-), carboxyl group (-COOH), amino (-NH₂) And / or similar functional groups on the surface of the membrane are present to increase the hydrophilicity. Furthermore, hydrophilicity is enhanced by microtexture phenomena, as described in Knight, Gryte & Hazlett. Such groups facilitate adsorption and / or absorption of water on the membrane. The hydrophilicity is particularly useful for filtering aqueous fluids.
[0032]
The preferred microporous membrane of the present invention is made from nylon. The term “nylon” encompasses films that form polyamide resins including copolymers and terpolymers. The polyamide resin includes a mixture of cyclic amide groups and different polyamide resins. Preferably, the nylon is a hydrolytically stable nylon, which is at least about 0 per mole of nylon as described in US Pat. No. 5,458,782, the contents of which are hereby incorporated by reference. .9 moles of amino end groups.
[0033]
In general, the various nylon or polyamide resins are all copolymers of diamines and dicarboxylic acids, or homopolymers of lactams and amino acids, but they vary greatly in crystallinity, solid structure, melting point, and other physical properties. Preferred nylons used in the present invention include copolymers of hexamethylene diamine and adipic acid (nylon 66), copolymers of hexamethylene diamine and sebacic acid (nylon 610), homopolymers of polycaprolactam (nylon 6) and tetra It is a copolymer of methylenediamine and adipic acid (nylon 46). The preferred polyamide resin is methylene (CH₂) And amide (NHCO) groups in the range of about 4: 1 to about 8: 1. Nylon polymers are available in a wide range of grades and vary within a range of about 15000 (average molecular weight) to about 42000 with respect to molecular weight and other characteristics.
[0034]
A highly preferred type of unit making up the polymer chain is polyhexamethylene adipamide, nylon 66, which has a molecular weight of about 30000. While polymers without additives are generally preferred, the addition of antioxidants, surfactants, charge modifiers or similar additives is useful under certain conditions.
[0035]
A three-band, reinforced, continuous, monolithic, geometrically symmetric microporous membrane made in accordance with the present invention has a porous carrier 12 as an important component. The retainer is at least substantially embedded within the intermediate band 16 of the membrane 10 to provide structural strength or reinforcement to the three-band membrane. The porous carrier 12 is prepared from a suitable material in a suitable manner. The retainer 12 provides the membrane with sufficient force to counteract the fluid pressure encountered during use without the microporous membrane 10 being damaged and deformed. The holding body 12 used here includes not only non-woven fabrics formed by extrusion, lamination, and the like, but also woven fabrics shaped like a grid or mesh. Other webs containing polymers are suitable as well, but the carrier 12 preferably comprises polyester, polypropylin, polyethylene, oliamide and polyvinylidene fluoride. The carrier 12 used in connection with the present invention is currently preferably formed from fibers with sufficient strength and uniformity, and evenly distributed in the crossweb and machine direction, with a high degree of structural integrity and Generally thin to provide a low pressure drop. See US Pat. No. 4,645,602 for an overview of the physical properties of the holder.
[0036]
In one presently preferred embodiment, when constructed according to the method of the present invention, the intermediate band 16 of the microporous membrane 10 is at least one of the upper band 18 and the lower band 20 of the membrane, and preferably the upper band. And an average pore size of both at least about 20 percent, preferably at least about 50 percent, more preferably at least about 100 percent, and most preferably at least about 200 percent. The pores formed in the intermediate zone 16 have an average size of about 10 microns or less, and the average pore size is preferably in the range of about 0.5 to about 2 microns, more preferably about 0.00. It is in the range of 1 to about 1 micron. Although not essential for full functioning, the intermediate zone 16 preferably has a fairly narrow range of pore size distributions.
[0037]
As long as the intermediate band 16 provides sufficient structural strength and embeds the retainer 12, the intermediate band 16 should be as thin as possible. This preferably currently prevents the fibers of the holding body from protruding from the intermediate band 16 into the upper band 18 or the lower band 20. However, in one preferred embodiment, the strands / fibers of the carrier 12 are in contact with or protruding from at least one of the other two bands 18, 20 formed from a dense dope or coating (coating) solution. Alternatively, when both bands are formed of dense dope, they protrude into both bands 18 and 20.
[0038]
It is believed that having a relatively thin intermediate zone where at least some of the scrim does not completely fit within the intermediate zone will keep the thickness of the intermediate zone to a minimum, resulting in an overall thinner final film. The thickness of the intermediate zone is typically in the range of about 50 to about 150 microns, preferably in the range of about 75 to about 100 microns, or substantially impregnated with a scrim that is impregnated at a particular time. It is the amount of dope necessary to do.
[0039]
In one presently preferred embodiment according to the present invention, the upper and lower bands 18 and 20 of the microporous membrane 10 comprise pores having a size that provides the desired filtration efficiency or particle removal. Generally, the average pore size of the upper and lower bands is about 1 micron or less, typically in the range of about 0.01 to about 1 micron. More preferably, the average pore size of each band 18, 20 is in the range of about 0.2 to 0.5 microns. The pore size distribution of the upper and lower bands 18 and 20 of the microporous membrane is preferably narrow. In an embodiment that yields particularly favorable results, the average pore size of the upper band 18 is substantially the same as the average hole size of the lower band 20. “Substantially the same” means that the average pore size of the upper band does not differ by more than about 25 percent from the average hole size of the lower band, and vice versa.
[0040]
One important feature of one preferred embodiment of a three-band, reinforced microporous membrane 10 made in accordance with the present invention is that it is geometrically symmetric about the central axis of the membrane 10 The upper band 18 and the lower band 20 have substantially the same thickness. The bands 18, 20 should be as thin as possible to minimize the pressure drop across the microporous membrane 10 while being thick enough to provide the desired particle removal. The individual thickness of each of the upper and lower bands ranges from about 25 to about 100 microns, preferably from about 35 to about 60 microns. The overall thickness of the reinforced, continuous, monolithic, geometrically symmetric microporous filtration membrane of the present invention generally does not exceed about 10 mils.
[0041]
The geometric symmetry of the microporous membrane 10 made in accordance with the present invention minimizes mechanical tension, reduces the possibility of delamination, and generally improves the structural integrity of the membrane. The above matters are particularly important in the fan-type pleated cartridge arrangement. In this arrangement, both sides of the microporous membrane are equally bent at the neutral axis of the reinforcing scrim. In the above bending, the tension is equally distributed, and a compressive force is applied to the pleat head and the recess. This eliminates excessive tension or compression loads on either side. The excessive tension or compressive load increases the possibility of damage and / or the possibility of damage to the membrane at the pleats. Furthermore, the unique thin cross-sections on both sides of the present invention have the advantage that the absolute radius from the center of reinforcement to the outer surface of the membrane is minimized, thus minimizing tension and compressive forces. However, it should be understood that the thickness of one of the upper band 18 or the lower band 20 is significantly less than the other thickness and is within the teaching of the present application.
[0042]
The completed reinforced microporous membrane 10 can be wound and stored for use under ambient conditions. The three-band, reinforced, continuous microporous membrane obtained from the present invention is made into a common commercial form such as a disk or pleated cartridge.
[0043]
In sterile filtration with biological fluids, the three-band, reinforced, microporous membrane 10 is or may be sterilized by autoclaving or hot water flushing. As mentioned above, especially when hydrolytically stable nylon is used, a three-band, reinforced, microporous membrane made in accordance with the present invention against the above types of treatment should be resistant. Has been found to retain structural integrity when used under the above conditions.
[0044]
The resulting three-band, reinforced, microporous membrane is easy to process and immediately forms a convoluted structure, such as a pleated shape. Due to the improved flow characteristics, the pump can be used directly on existing equipment without modification. In particular, with improved flow rates, existing pumps actually operate at lower loads and have a longer shelf life.
[0045]
The three-band, reinforced, filtration membrane 10 is characterized by an unexpectedly high flow rate for a given differential pressure, and is also characterized by durability, strength, uniformity, lack of pinholes and bubble defects. It is done. In many applications, the preferred membrane is used on the side of the membrane facing upstream.
[0046]
As shown in FIG. 2, one presently preferred method for preparing a three-band, reinforced, continuous, geometrically symmetric microporous filtration membrane of the present invention is the following: A porous retaining band 12 having a first side 22 and a second side 24 is provided, including a process, and currently preferably the first solution or dope 26 is pressure impregnated into the support 12 to provide a second solution or The dope 28 is coated on the third side surface 30 of the pressure-impregnated holding body 32, and the third solution, that is, the dope 36 is coated on the second side surface of the pressure-impregnated holding body 32. This allows a continuous microporous membrane having an intermediate band 16 disposed between the upper band 18 and the lower band 20 (see FIG. 1) from the first solution dope 26, the second dope 28, and the third dope 36. Will be formed. The holder 112 is currently preferably fully embedded within the intermediate band 16, which has a pore size that is at least about 20% larger than the hole size of at least one of the upper band 18 and the lower band 20. .
[0047]
The dopes 26, 28, 36 and cooling bath 28 used to make the reinforced microporous membrane 10 used here are conventional. Presently preferably, a new arrangement of slot dies 40, 42, 44 for first impregnating the holding body 12 with the first dope and then coating the other dope on both sides is particularly advantageous for producing the membrane 10. It turns out to be effective. A schematic diagram of one presently preferred apparatus useful for making the membrane 10 of the present invention is shown in FIG. The apparatus includes a first die 40 for pressure impregnating the retainer or scrim 12, a substantially opposite second die 42 and a third die 44. The second and third dies are for substantially simultaneously coating both sides 30, 31 of the initially impregnated scrim 12 or other device capable of coating the membrane as described above. It is.
[0048]
The three-band microporous membrane 10 generally has the first dope pressure-impregnated into the scrim and then one of many possible dopes including film-forming polymer in the solvent system. The dopes 26, 28, 36 are immediately cooled in a bath 38 that covers each side of the scrim and contains a conventional non-solvent system for the polymer. Important parameters that develop micropores (eg, pore size) in the membrane are not only the phenomena revealed in previously described patent applications, but also solvent systems used in polymers and non-solvent systems used in polymer films It is. Polymer solvent selection is determined by the nature of the polymer material used and can be determined experimentally based on solubility parameters, as is well known and routine in the art.
[0049]
The dope that forms the preferred nylon microporous membrane presently preferably includes a nylon polymer in the solvent system for the polymer. The solvent system includes a mixture of at least one solvent and one non-solvent for the polymer. Solvents that can be used with the alcohol-soluble nylon include lower alkanols such as methanol, ethanol and butanol and mixtures thereof. Non-alcohol soluble nylons are known to dissolve in acid solvents such as formic acid, citric acid, acetic acid, maleic acid and similar acids. The nylon dope after the composition is diluted with a non-solvent of nylon that can be mixed with the nylon solution. Non-solvent dilution leads to the initial precipitation value of nylon. The non-solvent is selected based on the nylon solvent used. For example, when a mixed aqueous nylon solvent is used, water is a non-solvent. In general, non-solvents are water, low alcohols such as methyl formic acid, methanol and ethanol, polyols such as glycerol, glycols, polyglycols, and ethers and esters, and mixtures of the above.
[0050]
The holding body 12 having the first side surface 22 and the second side surface 24 can be obtained by various techniques such as roll casting, spray coating (spray coating), slot die coating (slot die coating), and similar methods (slot die pressure). Impregnation is presently preferred) the first dope 26 is impregnated, thereby causing the carrier to substantially completely soak the first dope. As used in the present disclosure, “complete impregnation of the holding body” means that all the fibers of the holding body are completely surrounded by the liquid dope, the holding body has no portion not covered with the liquid dope, and the holding body Means that there is no portion protruding from the central band in the completed three-band film to the second or third band.
[0051]
The holding body 12 is held in a manner known in the art, preferably under tension, but the first dope 26 under stress penetrates and sufficiently penetrates the holding body 12. The impregnated support 32 is rolled and, if desired, the first coating solution is pushed into the support with a roller, as described in US Pat. No. 4,707,265, the contents of which are incorporated herein by reference. Thereafter, the second dope 28 is coated on the first side 30 of the impregnated holder 32 and the third dope 36 is applied on the substantially opposite slot die or one side of the dope-impregnated scrim. On the second side 31 using other suitable techniques, it is possible to coat the second dope and to coat the third dope essentially simultaneously on the second side of the dope-impregnated scrim. Covered. The application of the second dope 28 and the third dope 36 is currently preferably using simultaneous or substantially opposite slot dies 42, 44 simultaneously or substantially simultaneously so that the impregnated solution 32 is substantially Are supported by the mutual hydraulic power of the opposing slot dies 42,44. The slot dies 42, 44 into which the dopes 28, 36 are fed under pressure give particularly good results for applying the second dope 28 and the third dope 36 to both sides of the carrier 12 impregnated with the dope. . Preferably, the slot dies 42, 44 are arranged essentially opposite each other (see FIG. 2), through which the dope-impregnated holding body 32 passes. The second dope 28 and the third dope 36 are coated on each side 30, 31 and are currently preferably the same amount, but need not necessarily be coated with the same amount of dope.
[0052]
According to one preferred embodiment, the second dope 28 and the third dope 36 produce substantially the same pore size, but a different pore size than the first dope 26. According to another preferred embodiment, the second dope 28 and the third dope 36 not only create a different hole size than the first dope 28, but each also has a different hole size. It is possible to have a minimum pore size from a maximum pore size.
[0053]
  Thereafter, the first dope 26, the second dope 28, and the third dope 36 that are in direct contact with the cooling (quenching) fluid in the same cooling (quenching) tank 38 are simultaneously cooled on the outer surfaces of the second and third dopes ( Quench). The first dope 26 is currently preferably coarser, so it solidifies more slowly and comprises an intermediate band 16 (see FIG. 1) with relatively open holes, a three-band, continuous, monolithic This leads to the formation of symmetrical, geometric, microporous membranes. The intermediate band 16 is disposed between the upper band 18 and the lower band 20 having a dense hole size (hole diameter), or an upper band or a lower band having a relatively open hole size, and a denser hole size. It is arrange | positioned between the upper belt | band | zone which has (hole diameter), or a lower belt | band | zone. After the microporous membrane is formed, the membrane is washed and dried to yield the final product as shown in FIG.
[0054]
The shape of the nose of the first die used to compress and impregnate the scrim has now been determined to be important, preferably to achieve substantially complete impregnation or scrim penetration. In particular, to obtain complete or substantially complete impregnation of the scrim 12, the relative position of the scrim on the nose of the die 40 is such that the upper die surface in contact with the scrim is straight, as shown. It is generally shown in FIG. 2 except that it is arched. In particular, the upper portion of the die 40 is currently preferably arched at an angle that the scrim 12 forms with the die and is between about 5 ° and about 65 °. In one aspect of the invention, it is important that the first dope 26 substantially completely impregnates the scrim 12, so the relative position of the upper surface of the die 40 is important and the scrim is completely or Not only is it substantially completely impregnated and immersed in the first dope, but currently, preferably a sufficient amount of fluid dope extends beyond the fibers of the scrim 12. Thereby, all fibers are currently preferably coated with at least one mole of fluid dope before the scrim, impregnated with the first fluid dope and coated with substantially the same second and third dopes. To have.
[0055]
Furthermore, after scrim is impregnated and coated on both sides with the dope, it is important to prevent or at least minimize the vapor from the cooling bath from contacting the dope, for example in the vapor control zone. Such means are provided to prevent or minimize the interaction of the cooling bath vapor with the coated scrim prior to cooling. This vapor control zone prevents the dope from solidifying at the bottom of the die and is necessary to prevent the dope from contacting the vapor before the dope reaches the cooling bath, as is known in the art.
[0056]
However, in another aspect of the invention, it is also important that the scrim is impregnated with a predetermined amount of the first dope and that at least a portion of the scrim is not completely covered by the fluid dope. In such a case, at least one fiber of the scrim or a part of the fiber is at least in contact with or slightly protruding from at least the second and / or third doped band. When making a three-band membrane with the same pore size on both sides of the central band, both sides of the dope impregnated in the scrim have at least a portion that contacts or protrudes from the vapor fluid dope surface after the scrim is impregnated. Yes. Incomplete encapsulation of the scrim with the first dope, or a finished 3 having parts / fibers of the scrim that protrudes or touches both the second and third bands or one band with a denser pore size. Get a banding membrane.
[0057]
When making a three-zone membrane with three different pore size dopes, the side of the pressure-impregnated scrim that is coated with a dense dope has a part that exceeds the level of dope impregnating the scrim, and the scrim is pressure After impregnation and before the scrim is coated with the dense dope, the surface tension of the fluid dope that substantially impregnates the scrim is broken.
[0058]
The above method is carried out continuously or batchwise on many representative devices. Generally, the carrier 12 in the form of a nonwoven fiber scrim is unwound from the roll under tension and pressure impregnated with the first dope 26 as described above. The pressure-impregnated holding body 12 is then coated with the second and third dopes on each side face 30, 31 as described above. In order to form a three-band, continuous, microporous membrane of the present invention from the first, second and / or third dopes, the uncooled dope / scrim bond is substantially free while tension is in the cooling bath. Immediately soaked in. The microporous membrane is then dried and wound onto a roll under tension for storage as is known in the art.
[0059]
The scrim impregnation is considered to be the speed of the scrim relative to the initial die and the dope, which affects the viscosity effect of the dope, the back tension of the scrim (back tension), the dope pressure. Each of these parameters is specific to the particular scrim impregnated with the dope and is determined by one skilled in the art.
[0060]
By way of example, as will be appreciated by those skilled in the art, if the speed of the first dope is too low, the first dope lacks tackiness and the ability to be immediately coated with the second and / or third dopes. . If it is too viscous, the first dope will not be fully impregnated into the scrim, and the scrim will keep the first dope excess on the die side of the scrim, and will be adequately spaced away from the scrim. It does not penetrate.
[0061]
As shown in FIG. 3, one exemplary apparatus 50 useful for performing the method of the present invention includes a continuous scrim or other structure for containing polymer dopes 26, 28, 36. The conventional assembly 52 is included. Conventional assemblies typically include a release station that includes an unwinder. The unwinder includes a spindle for providing one or more holders, and a brake element conventionally used to unwind a continuous sheet of associated release and holders. The assembly 52 also includes a number of conventional release rollers that begin to adapt to the movement of the scrim through a ladder device that includes a series of rollers, as the series of rollers are known in the art, Further, the scrim is prepared so that the position can be adjusted and tension can be applied to the scrim and the impregnation operation can be performed.
[0062]
As the scrim 12 exits the conventional ladder device, the scrim enters the conventional drive area. The drive area includes many individual rollers. At least one of the rollers is driven to pull the scrim 12 from the conventional release department. In addition, the rollers are provided and arranged to define the tension within the scrim 12 and the position of the scrim 12 as is known to those skilled in the art.
[0063]
The scrim 12 is fed downstream by a conventional drive zone, currently preferably between a series of dies. The series of dies is preferably a first die in which the scrim is completely pressure-impregnated with the second dope 26, and a second die in which the second dope 28 and the third dope 36 are coated on the outer surface of the dope-impregnated scrim. 42 and a third die 44. In a preferred embodiment in one apparatus of the present invention, the first die 40 is a single slot die and is operably connected to a suitable reservoir 60 containing a first dope. The first dope varies depending on the film forming type used, but is generally a formulated fluid dope and is processed to create a specific pore size upon cooling. A conventional control pump mechanism (not shown) selectively operates to carry the first dope 26 from the reservoir 60 to the first die. The first die 40 has an open shape, is provided with a uniform amount of the first dope 26, and pressure-impregnates the scrim 12 as the scrim 12 opens and passes through the first die 40. When different sizes of scrim 12 are used, the die 40 is changed for proper scrim impregnation. As described above, the dope 26 conveyed to the scrim 12 is substantially completely impregnated into the scrim, that is, immersed in the scrim.
[0064]
After the scrim 12 is at least substantially impregnated or soaked with the first dope, the scrim moves between the second die 40 and the third die 44. In one embodiment of the device, the scrim 12 is arranged vertically and moves in the downstream direction. In one presently preferred embodiment of the device, the scrim 12 initially moves at an angle of 90 ° or less, as shown in FIG. The second die 40 and the third die 44 are arranged essentially on opposite sides of the scrim 12 in a preferred manner. The second die 42 is oriented to coat the polymer dope 28 onto the desired first surface of the substantially immersed scrim 12 and the third die 44 is substantially immersed in the polymer dope 36. Oriented to cover the desired second surface 24 of the scrim 12. Each die 42, 44 is fed from a reservoir 62, 64 having dopes 28, 36. The dope includes, for example, nylon 66 dissolved in formic acid. In that case, the desired polymer membrane is nylon and exactly the same. It is recognized that the dope is a combination of a well-known film-forming polymer in a suitable and well-known solvent. A conventionally controlled pump mechanism (not shown) selects to carry the dopes 28, 36 to the dies 42, 44.
[0065]
As best shown in FIG. 3, the dies 42, 44 are respectively disposed on opposite sides of the pressure impregnated scrim 12 and essentially face the other die. Each die 42, 44 has a chamber 76 for receiving the dope solution and a narrow slot 74, extending across the front 75 side of each die, and the scrim 12 (die) impregnated with the dope solution. 40) A scrim that has been transported over and then substantially immersed is coated on both sides (die 42, 44). The dope is pushed out of the slot 74 in a manner known in the art by pressure provided by a conventional storage pump (not shown). The pressure exerted on the dope varies with each dope and the scrim used. It is known to those skilled in the art to determine the appropriate pressure for the dope applied to a particular scrim. The dies 42, 44 are positioned substantially close to the immersed and impregnated scrim 12 and the dope is ejected from the slot 74. This makes direct contact with the outer surface 22 of the scrim 12 soaked with the dope. As can be seen in FIG. 3, the length of the slot 74 determines the final width of the dope coated on the soaked scrim. By means of a mask or other means, it is possible to coat the dope at the end of the scrim 12, leave the fringing ear region 76, pot, or eliminate other secondary forming operations. Unlike the other dopes, the initial dope can have three different dopes, the first dope impregnating the scrim 12, the second dope and the third dope of the scrim impregnated with the first dope. It should be understood that a three-band membrane is obtained with a graded density coated on each side.
[0066]
In a similar manner, although not shown, the intermediate region along the slot 74 may be masked to accommodate final filtration purposes and devices where the reinforced, continuous membrane of the present invention is used. The internal shape of the first die 40 is similar and will therefore not be disclosed in greater detail. However, as will be appreciated by those skilled in the art, it may be important that the first die 40 is arranged to be substantially completely immersed in the scrim 12.
[0067]
As shown in FIG. 2, after all three dopes have been applied to the scrim 12, the resulting uncooled scrim reinforced structure is directed to a cooling device 38. The cooling device 38 is conventional and includes a conventional reservoir that circulates a large amount of non-solvent and is referred to as a melted polymer cooling bath that pushes the polymer into each of the three dope zones for subsequent solidification. As a result of cooling, a continuous, non-laminated geometry that includes one band of microporous polymer 18, 20 on each side of the intermediate band 16 of the microporous membrane enclosing the carrier 12 (see FIG. 1) A reinforced membrane 10 is obtained which is symmetric in terms of science. Since the polymer layers 18, 20 had been coated and cooled substantially similarly before contacting the rollers or other equipment that impeded the solidification of the doped polymer during cooling, the three-band membrane 10 is Is symmetrical. After the polymer has solidified in the cooling bath, the membrane 10 passes over a conventional first roller in the cooling bath. The membrane 10 is conventionally pulled around a second roller that is driven by a conventional drive means (not shown) through the cooling bath. At this time, formation of the synthetic film 10 is completed, but excess fluid from the cooling bath 38 remains there.
[0068]
As shown in FIG. 2, the scrim 12 with three separate layers of operably applied dope is immersed directly in the cooling bath 38. For the purposes of this disclosure, the term direct refers to the contact or interaction of the impregnated and coated scrim with the device 50, or other solid element, between the roller or die 40, 42, 44 and the cooling bath 38. It means not. Thus, direct refers to the length of time required for the impregnated and coated scrim to move from the coating dies 42, 44, and the physical distance between the coating dies 42, 44 and the cooling bath 38. Not shown. However, it is preferred that the distance and time be as short as possible consistently to produce a fine film. In addition, after scrim is impregnated and coated on both sides by means such as a dope, for example a vapor control zone, it is important to prevent vapor from the cooling bath from contacting the dope or to minimize vapor . This vapor control zone, as is known in the art, needs to prevent the dope from solidifying on the bottom of the die and to cool the dope with steam before reaching the cooling bath.
[0069]
The newly formed membrane 10 currently preferably displaces the liquid overflowing from the cooling water immediately in a conventional first stage rinse apparatus. Thereafter, as is known in the art to complete the rinsing of the membrane 10, the membrane travels over many rollers and the tank 72 enters the reverse fluid wash tank 72. Includes a reservoir containing a lot of water, a number of rollers to increase the contact time of the membrane 10 in the tank 72 and appropriate sprawl and circulation devices. As the membrane 10 exits the wash tank 72, it enters a conventional winding section where it is rolled up onto a spindle for storage and drying and the like, as is known in the art.
[0070]
As is apparent from the drawings and the foregoing, the dies 42, 44 are now positioned to face each other, preferably simultaneously, so as to simultaneously cover both sides of the substantially immersed scrim, with the scrim extending vertically therebetween. Pass through. A scrim substantially immersed on both sides with a dope emanating from the die is passed through a distance towards the cooling device and impregnated and coated scrim is preferably controlled by a controlled atmosphere. . The distance is controlled by the movement of the dies 40, 42, 44 and can be easily controlled by lowering or raising the level of cooling fluid in the tank. By controlling this distance, the vapor zone is controlled to form a microporous film.
[0071]
Once traversed the distance to the cooling tank, the impregnated and coated scrim is immersed in the impregnated cooling fluid. The coated scrim will pass a predetermined distance in the cooling device, as is known in the art, before reaching the first roller.
[0072]
An important aspect of the present invention is that the impregnated and coated scrim does not fit the roller or the solid or physical elements of the device at this stage. The stage is the stage prior to solidifying the three bands of dope to such an extent that the film develops sufficient concentration to avoid or prevent deformation that occurs during subsequent stages of the manufacturing process. . Thus, the first predetermined distance and the second predetermined distance act together and comprise means to allow solidification on the impregnated and coated scrim, the scrim having a polymer film during subsequent manufacture of the synthetic film. Avoid and prevent damage and deformation. By the above, the membrane bands 18, 20 are substantially uniform in thickness and are selected by the pore structure and, optionally, the dope and cooling solution, and the temperature, concentration, ratio of coated scrim through the device. Surely bring the right size.
[0073]
In general, the residence period during which the impregnated and coated scrim travels in the cooling tank 38 is related to the impregnated and coated scrim travel speed, temperature, and cooling fluid concentration and tank height. Accordingly, the bottom of the tank is equipped with rollers, as is known in the art, to reverse the direction of movement of the coated scrim, ie upward, outward from the tank.
[0074]
Upon exiting tank 38, the cooled membrane is washed for the purpose of removing excess cooling fluid. The apparatus includes a first stage rinsing device 70 and a back fluid wash tank 72 as described above. Thereafter, as is known in the art, the membrane structure is rolled up and dried for subsequent use.
[0075]
Example
Dope preparation
Two dopes are prepared using the method described in US Pat. No. 4,707,265, Example 1. The dope is 14.5 percent nylon 66 by weight (Monsanto / Solutia Vydyne^R 66B) Made with polymer. The characteristics of the prepared dope processed as an unreinforced film with a standard dry bilayer are given in Table 1.
[0076]
[Table 1]

[0077]
Example 1
A geometrically symmetrical, pore size symmetric continuous three-band membrane with “open” (large pore size) scrim impregnation was prepared as follows.
[0078]
A scrim suitable for preparation of a nonwoven polypropylene heterophasic fiber web or the present invention (commercially available at Freudnberg, Viledon, Grade # F02432) has a nominal weight of nominally 30 grams / square meter and is taught in this application Was processed by the method. The scrim is pretreated with a mild corona discharge to increase wettability before being pressure impregnated. A larger pore size dope 97L038 was used to pressure impregnate the web with a nylon solid impregnation weight of about 7 grams / square meter. The nylon solid comes from nylon dissolved in the dope solution. The dope solution is, for example, a 14.5% nylon solution (approximately 50 grams of fluid dope per square meter), and the amount of solution is impregnated with a void volume, filled, and integrated with a holding scrim. A first band with a large hole size is made. Upon pressure impregnation of the scrim with 97L038 dope, both sides of the pressure impregnated scrim are coated with a uniform layer of small pore size dope, 97L028, essentially simultaneously. In the above example, the total coating weight carried on the two sides is about 37 grams / square meter nylon solid in 14.5% solution (approximately 260 grams fluid dope per square meter), Divided into two streams of dope fed on two sides. As a result, both sides are substantially uniformly coated with the same dope, creating second and third bands of small pore size dope. The division of the 97L028 dope amount was not complete in that one side of the impregnated scrim received approximately 15 grams / square meter of nylon solid and the other received approximately 22 grams / square meter of nylon solid. The imbalance in the amount of coated dope on the two sides results in a slight imbalance in the small pore sizes that define the band to be coated, but this imbalance is inconsistent with the performance of the final product. Does not bring profit. The total application of both dopes was approximately 44 grams / square meter nylon solid. The coated three-band structure is then in rapid contact with the Marinaco-type cooling solution. The three-band structure is cooled simultaneously from the outer surface of 97L028, which is a small pore size dope. Thereby, a continuous microporous membrane structure was formed. The cooled membrane was then washed, dried with dimensional stability in the X & Y direction, and tested in the usual manner. The test results are shown in Table 2.
[0079]
4a-4f are electron micrographs of the cross section of the film made in Example 1. FIG.
[0080]
Example 2
A three-band membrane of geometric symmetry and asymmetric pore size was prepared as follows.
[0081]
The second three-band membrane is identical to Example 1 except that one of the coated surfaces of the pressure-impregnated scrim is coated with the same approximately 22 grams / square meter nylon solid from a large pore size dope 97L038. Prepared in almost exactly the same way. The opposite side (Zone 3) was coated with approximately 22 grams / square meter of nylon solid from a small pore size dope 97L028. After cooling the two sides simultaneously, washing and controlled drying, the resulting final membrane is It is substantially geometrically symmetric to the neutral axis of the continuous, reinforced scrim, but has very different pore size characteristics on both sides of the scrim (eg, pore size asymmetry). It is shown in 2.
[0082]
5a-5f are electron micrographs of the cross section of the film made in Example 2. FIG.
[0083]
Example 3
A controlled and reinforced membrane (single dope, three strips) was prepared.
[0084]
Controlled and reinforced membranes were made compared to reinforced membranes made according to the method of the present application. This three-band, reinforced membrane is exactly the same as the membrane made in Example 1, except that the first pressure-impregnated zone was made using a small pore size dope 97L028. Thus, all three bands are built using a single dope and divided into three streams to each die. After cooling the two sides simultaneously, washing and controlled drying, the resulting membrane was a continuous, substantially geometrically symmetric, single pore size structure membrane. The membrane is similar in shape and acts on a standard single layer reinforcement membrane common to today's nylon microporous membrane industry. The test results for the membrane are also shown in Table 2.
[0085]
[Table 2]

[0086]
Example 1 to Example3
As can be seen from Table 2, the membrane of Example 1 has a clearly improved flow rate over the standard membrane. Pure water flow rate (nominal 47mm test disc (13.5cm at 5psid water pressure²Q) representing clean de-ionized water at cc / min relative to the test area) shows an improvement of about 20% but is measured at the initial bubble point at the same overall thickness. Concentration increased by about 6%. The improvement has two potential advantages. The benefits are improved clean water flow and improved concentration as measured by IBP. The increase in initial bubble point is confirmed by both an increase in the total foam point of the membrane and a decrease in the ASTM average pore size ratio.
[0087]
The membrane of Example 1 represents an advantage of the present invention. There are two geometrically symmetric, independent, definitive bands of small pore size membranes, which give the highest concentration due to excess deterministic layers and are separated by unrestricted inner bands. The unrestricted inner zone includes a reinforcement and has a surprisingly thin cross-section overall without degrading the performance of the deterministic layer.
[0088]
The membrane of Example 2 has a great improvement in flow rate over the standard (control) membrane of about 78 percent, but retains the same concentration characteristics in IBP and FAOP. The more generally recognized method, average pore size (MFP), is the average pore size of the average flow hole (MFP) that FAOP approximates, and the larger the average flow hole that shows the expected difference, Consistent with higher flow rates, and compared to the control membrane, the flow average method shows that the pore size of the membrane of Example 2 is more widely distributed. However, while having a single maximum pore rating on the membrane, it has the same initial bubble point, the standard on which the microfiltration industry is based to test the integrity of the membrane. Does not reduce importance. Therefore, Example 2 shows another advantage in the membrane of the present invention. The advantage has the ability to provide new, surprisingly thin cross-section reinforced unfiltered and final filtered when reducing pore size. The performance is the ability to make three separate bands within a single membrane, is geometrically symmetric, has good concentration and very high flow rate.
[0089]
Example 4
The dope used in this example was prepared as in the first three examples. The dope was made using nylon 66 (Monsanto / Solutia Vydyne 66Z) polymer. The characteristics of the dope processed as a standard, dry, two-layer unreinforced film are given in Table 3.
[0090]
[Table 3]

[0091]
Another geometrically symmetric, reinforced three-zone membrane with "open" (large pore size) scrim impregnation was prepared.
[0092]
A spunbonded web of nonwoven fiber suitable for preparation of the present invention (commercially available from Ahlstrom, tradename Hoolytex, Grade # 3257) is nominally 32 grams per square meter Has weight and was selected for processing. The processing method was essentially the same as that disclosed in Example 1. The differences were as follows. One zone is pressure impregnated with a large pore size dope 97A016 having an impregnation weight of nylon solids of about 6 grams / square meter. Bands 2 and 3 were coated at the same time with a substantially uniform layer of 97A012, a small pore size dope. In this example, the total coating weight carried on the two sides is about 19 grams / square meter of nylon solid, and this total amount is divided substantially evenly on the two sides so that both bands are Received a coating of about 8 to about 11 grams / square meter. Cooling, cleaning and testing appear to be in the previous example. The test results for the membrane are shown in Table 4. At the same time, the control film was processed, and a small hole size dope 97A012 was used not only in the second and third bands but also in the first band. The control film test results are also shown in Table 4.
[0093]
[Table 4]

[0094]
Discussion of Table 4
A three-band, reinforced microporous membrane with a very thin cross-section was made as described above. The above example demonstrated a reinforced band and two very thin definitive bands, with a fairly high concentration membrane. It should be noted that the thickness of the filled Hollytex scrim is approximately 3.5 mils. Therefore, the remaining 1.2 mil of the 4.7 mil of Example 4 was divided into 2 and 3 bands, leaving an effective definite membrane of only about 0.6 mil on each side of the reinforced band. It is. However, this thickness can provide a flow rate improvement of about 55 percent compared to the control membrane and only loses about 12 percent concentration.
[0095]
Example 5
The dope used in this example was prepared as described above. The dope was made using nylon 66 (Monsanto / Solutia Vydyne 66Z). The characteristics of the dope processed as a standard dry two-layer discontinuous film are given in Table 5.
[0096]
[Table 5]

[0097]
Another geometrically symmetric pore size reinforced three-band membrane with "open" (large pore size) scrim impregnation was prepared as follows.
[0098]
The same substrate was used in Example 4 (Hollytex 32547) and the processing method was essentially the same as the method disclosed in Example 1. However, Zone 1 was pressure impregnated with a large pore size dope 97B011 having a nylon solid with an impregnation weight of about 6 grams / square meter. Bands 2 and 3 were coated with a substantially uniform layer of 97B024, a small pore size dope. In this example, the total coating weight carried on the two sides was about 38 grams / square meter of nylon solid. As a result of the overall coating weight carried being divided between the two sides, both layers 2 and 3 were subjected to a nylon solid coating process of about 17 to about 21 grams / square meter. The total application of both dopes (large pore size and small pore size) was approximately 44 grams / square meter of nylon solid. Cooling, washing, drying and testing were performed as described above. The test results of the obtained film are shown in Table 6. During the same experiment, the control membrane was fabricated with a small pore size dope 97B024 in all three bands. The test results of the control film are also shown in Table 6.
[0099]
[Table 6]

[0100]
Discussion of Example 5
As can be seen from the table, compared to Example 4, the nominal higher coating weight used to form the definitive bands 2 and 3 of Example 5, which is this example, has a higher concentration. Create a film. The membrane comprises an IBP within about 5 percent of the control membrane and a flow improvement of about 53 percent compared to the control membrane.
[0101]
Example 6
The dope was prepared as described above. The dope was made using nylon 66 (Monsanto / Solutia Vydyne 66Z) polymer. The characteristics of the dope processed as a standard dry two-layer discontinuous film are given in Table 7.
[0102]
[Table 7]

[0103]
Another geometrically symmetric, pore size reinforced three-zone membrane with “open” (large pore size) scrim impregnation was prepared.
[0104]
The same substrate as in Example 4 was used (Hollytex^R 3257). The processing method was the same as the method disclosed in Example 1. However, one band was pressure impregnated with a large pore size dope 97B067 having a nylon solid impregnation weight of about 6 grams / square meter. Bands 2 and 3 were simultaneously coated with a substantially uniform small pore size dope, 97B066 layer. In this example, the total coating weight carried on the two sides was about 24 grams / square meter. The total coating weight carried was divided between the two sides. This yielded a nylon solid membrane of about 11 to 13 grams / square meter for both bands. The overall application of both dopes was approximately 30 grams / square meter of nylon solid. Cooling, washing, drying and testing were performed as in the previous example. The test results for this film are shown in Table 8. During the same experiment, the control membrane was fabricated using a small pore size dope 97B066 in all three zones. The test results of the control film are also shown in Table 8.
[0105]
[Table 8]

[0106]
Discussion of Example 6
Again, compared to Example 4, the nominally higher coating weight of the definitive bands 2 and 3 in this example produces a very concentrated film. The membrane has an IBP within about 1 percent of the control membrane and a flow rate that is about 35 percent improved over the control membrane.
[0107]
The specific embodiment described above shows a 0.1 micron membrane and is suitable for use in the electronics industry to purify water for semiconductor and integrated circuit manufacturing. The increased flow rate of new membrane clean water resulting from the new processing described in this application allows for a smaller design, less expensive processing system when building a semiconductor production plant. This results in the same high quality final water at the design demand flow rate.
[0108]
Summary of Examples
The three-zone membrane of the present invention is characterized by a significant improvement in flow rate in filtration applications due to the pore size characteristics compared to standard products common in the membrane filtration industry. A three-band relatively thin cross-section, membrane product provides a membrane cartridge with a larger surface area and higher throughput. This translates into additional products of higher value for filtration customers.
[0109]
A very general experiment with the substrate, pretreatment, band coating weight, dope viscosity, pore size, and band positioning with respect to pore size yields an optimized membrane product, which is an existing membrane product. With better performance. Other membrane applications that benefit from the ability to customize band performance include (by way of example) diagnostic products using human fluids, transfer membranes, separation devices, medical devices, and other obvious to those skilled in the membrane arts Includes device.
[0110]
As clearly shown in FIGS. 4a-h, a three-band, supported microporous membrane made in accordance with the present invention has three separate, continuous bands. Also, as clearly shown in FIGS. 4b-4d, at least a portion of the scrim contained within the central band is at least partially in both the upper band and the lower band (the same band having a smaller pore size). Stick out.
[0111]
As clearly shown in FIGS. 5a-h, a three-band, supported, microporous membrane made in accordance with the present invention comprises three separate, continuous bands (zones). Also, as clearly shown in FIGS. 5b-5d, at least a portion of the scrim contained within the central band (the band with the largest hole size) is the lower band (the band with a smaller hole size). Protruding at least partially.
[0112]
Based on the above, the method of the present invention that mixes the dope in the fluid results in a newly improved three-band, continuous membrane.
[0113]
Based on the foregoing, it is clear that the above objective is accomplished using the apparatus and process for making the three-band, reinforced membrane described herein. Various having at least a single layer holder at least substantially embedded within the first zone of the microporous membrane and comprising at least one zone (zone) of the microporous polymer membrane on each opposing surface of the first zone It will also be apparent to those skilled in the art that the course of the present invention is carried out to produce a microporous membrane. Similarly, not only the speed at which the scrim is continuously delivered to the apparatus, but also the dope cooling solution, concentration, and temperature can be readily determined by those skilled in the art.
[0114]
The three-band membrane of the present invention comprises a discontinuous pore structure having a continuous entanglement of polymer separation layers / bands. This substantially integrates the produced continuous microporous membrane.
[0115]
After formation of the three-band, reinforced, microporous membrane 10 of the present invention, the membrane is processed according to US Pat. No. 4,473,474, the disclosure of which is hereby incorporated by reference to produce electronic components. A positively charge-modified microporous membrane that is particularly suitable for filtering the high purity water required for the production of each of which is incorporated herein by reference.
[0116]
Although experiments have not yet been performed to demonstrate that the present invention has the same or similar results when using other triple phase inversion polymers, the present invention has similar chemical structures and structures. Because of this, many triple phase inversion polymers are currently believed to be effective in processing for membranes or other useful purposes. In particular, nylon 66 is a number of polymer groups that can be processed into a microporous membrane by phase inversion treatment. Thus, the above course is likely to apply the method and system of the present invention to other polymers. The polymers include, but are not limited to, nylon 66, nylon 46, nylon 6, polysulfone, polyethylsulfone, polyvinylidene difluoride, and other triple phase inversion polymers that form a microporous structure through the phase inversion process.
[0117]
While the invention, apparatus and method for making what constitutes the preferred embodiment of the invention constitutes the preferred embodiment of the invention, it is not limited to the exact apparatus or method itself, but is explicitly defined in the appended claims. Modifications may be made without departing from the scope of the present invention.
[Brief description of the drawings]
1 is a cross-sectional view of a membrane according to the invention.
FIG. 2 is a schematic diagram of the method and apparatus of the present invention.
FIG. 3 is an enlarged perspective view of a web disposed between opposing dies of FIG. 2, wherein a portion of one die is partially cut.
FIGS. 4a-h are electron micrographs of a three-band microporous membrane of the present invention, representing the inner surface of the three hole bands at 100X, 300X, 500X, 1000X and 2500X.
FIGS. 5a-h are electron micrographs of a supported three-zone microporous membrane of the present invention, representing the inner surface of the three pore zones at 100X, 300X, 500X, 1000X and 2500X.
[Explanation of Symbols] 10 Membrane, 12, 32 Holder, 16 Intermediate Belt, 18 Upper or Second Belt, 20 Lower or Third Belt, 22 First Side, 24 Second Side, 26, 28, 36 Dope, 40 , 42, 44 Die, 70 Rinsing device, 72 Reverse fluid wash tank, 74 slots.

Claims (10)

Providing a continuous holding material (12) having a first surface (22) and a second surface (24);
Disposing first die means (40) relative to the retaining material (12);
In order to form a first pore diameter in the intermediate layer (16) of the three microporous membrane (10) using the first die means (40), the first polymer dope (26) is A step of pressure impregnating the holding material;
Placing two opposing second die means (42) and third die means (44) downstream of said first die means (40);
Using the opposing second die means (42) and third die means (44), at least one in two other layers (18, 20) of the three microporous membranes (10). To form two additional pore sizes, both sides (30, 31) of the holding material (32) impregnated with the first polymer dope (26) are simultaneously coated with at least one additional polymer dope (28). as is, the step of passing said first polymer dope (26) is pressurized圧含soaked holding material (32) between the second die means for the facing (42) and third die means (44) When,
A process for producing a three-layer continuous, reinforced microporous membrane for separation treatment (10) comprising:   The manufacturing method of Claim 1 including the process of providing a controlled vapor zone.   The at least one additional polymer dope is adjusted to form the same pore size and the first polymer dope is adjusted to form a different pore size from the at least one additional polymer dope; The manufacturing method according to claim 1.   The at least one additional polymer dope includes a second polymer dope and a third polymer dope each adjusted to form a different pore size, and the first polymer dope comprises the second polymer dope The manufacturing method according to claim 1, which is adjusted so as to form a different pore size from the dope and the third polymer dope. Providing a quench means comprising a non-solvent of at least two different polymer dopes;
Doped coating, a step of transferring and doped impregnated retaining material in the quench unit,
To form the intermediate layer and the microporous membrane which is continuous reinforced with two outer layers, the polymer, such that sufficiently precipitated out and coagulation to avoid deformation in subsequent manufacturing, and doped coating It doped impregnating the steps of quenching the holding material having at least two different polymer dope within the quench unit,
The manufacturing method of Claim 1 containing this. Providing a porous retaining material (12) having a first surface (22) and a second surface (24);
Impregnating the holding material with a first dope (26);
Coating the first surface (30) of the impregnated retaining material (32) with a second dope (28);
Coating on the second surface (31) of the impregnated holding material (32) simultaneously with the step of coating with a third dope (36);
As a result , a continuous microporous membrane having an intermediate layer (16) disposed between the upper layer (18) and the lower layer (20) is formed from the first dope, the second dope and the third dope. Wherein the retaining material is embedded in the intermediate layer (16), the intermediate layer (16) being at least 20% larger than the pore size of at least one of the other two layers (18, 20) Has a pore size,
A method for producing a three-layer, reinforced, continuous, geometrically symmetrical microporous membrane for separation treatment (10) comprising: Providing a quench means including a non-solvent for the film-forming polymer;
Transferring the coated retention material to the quench means;
Quenching the coated retention material having at least two different polymer dopes in the quenching means;
As a result , the polymer precipitates and solidifies sufficiently to avoid deformation during subsequent manufacturing, thereby forming a three-layer, continuous microporous membrane ,
The manufacturing method of Claim 6 containing this. Means (52) for supplying a continuous holding material (12);
First die means (40) disposed relative to the retaining material for impregnating the retaining material with a first polymer dope (26);
Since the dope is simultaneously coated on each opposed surface of the impregnated retaining material (32) (30, 31) on at least one additional polymer dope (28), downstream of the first die means (40) Opposing die means of the second die means (42) and the third die means (44) disposed ;
For producing a three-layer, reinforced composite microporous membrane (10) for separation . The first die means, said second die means, and to simultaneously quenching the dopes provided by the third die means, the quenching means disposed downstream of the second die means and said third die means Contains
The quench means includes a non-solvent of polymer dope so that the coated holding material forms a three layer reinforced microporous membrane on both sides of one dope in the middle of the holding material. at least one of the at least two different doped with additional doping a sufficient time to precipitate out and coagulation, is treated with a non-solvent in the quench unit, apparatus according to claim 8. To avoid deformation during subsequent processing of the microporous membrane, for sufficiently solidifying the polymers of at least one doped coating the different dope on to saturate the retaining material, the means associated with the quench unit 9. The apparatus of claim 8 , comprising.

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